Display driver problem?

I have been having some issues with my monitor and I am trying to determine if I need a new monitor or if it's an issue with my PC.

Every couple days my screensaver quits working and the monitor screen is just black. When I strike a key or move the mouse there is no response on the screen, I don't get a picture to come up, so the only way to get my computer to respond is to hold the power button down to shut it off. Obviously I don't want to keep shutting off the computer that way. One time as I was sitting at my desk reading (waiting for something to download) the screensaver was running and I noticed that it "froze", so I immediately moved the mouse and the screen came back up with a picture and a message that said something like "Your display driver failed but managed to recover itself". The message has not come up again, so that is the best summary I can give. i don't know if there was an error number given, or the exact wording of the message, but it was something like that.

My husband thinks that we have a virus, but I have run several virus/spyware scans in addition to my normally scheduled scans. I have Comodo for a firewall, and I use AVG for antivirus and SuperAntiSpyware for anything else. I do not think it's a virus problem. I think we either need a new monitor or that we have a driver that needs to be updated.

I have a Dell Monitor, a tube monitor, not a flat screen. I have an Acer computer and we are running Windows Vista. Any suggestions would be helpful.